The use of organic solvents such as hexane, heptane, alcohols, water, and other liquids in processing chemicals or materials for industrial and consumer use is generally known. Within these general processes there are many known specific processes in which an organic solvent comes into contact with and/or contaminates solid particles or granules which are also utilized in that specific process.
A first example of a specific process which utilizes an organic solvent which comes into contact with and contaminates solid particles is the process for the extraction of oil from oil seeds. Upon preparation of the oil seeds, the particles are contacted with the hexane to extract the oil. A quantity of the hexane remains entrained or entrapped within the solid particles, and thus, requires desolventizing prior to further processing of the oil depleted particles.
A second well known process in the chemical industry is to utilize fixed-bed treatment systems, wherein a mass of particles, such as resinous beads or catalyst particles, are placed within a containment vessel through which other compounds flow for treatment or reaction as effected by the fixed-bed particles. Subsequent to processing a given quantity of material, the fixed-bed material must be removed. Upon removal, the particles, which are at times contaminated with organic solvents or other liquids, must be desolventized prior to disposal or reuse.
A third example of a situation wherein solid particles become contaminated with a solvent or hydrocarbon and must be desolventized includes the accidental contamination of soil from a spill of solvent or hydrocarbons. Examples which are well known include leaking underground storage tanks, or accidents related to the bulk transfer of chemicals via trailer or rail car. Soil contaminated with organic solvents must be desolventized to prevent leaching of the solvent into the ground water or to prevent further human contact.
Presently available desolventizing equipment is not designed for handling solids which can be abrasive. Abrasive solids would destroy a typical desolventizing unit equipped with sweep arms. Further, available desolventizing equipment utilizing sweep arms and paddles are not designed to completely remove the solids off the plates by each passing paddle. The increased residence time for isolated solids can cause burning of the solids to the hot decks and can greatly increase the grinding or breaking up of the solids as they are conveyed and mixed.
Accordingly, the need exists for a method and apparatus for efficiently removing solvents from a mass of particles contaminated therewith. An apparatus and method to remove such solvents should be designed to process abrasive particles. Further, such apparatus should be designed so that solids which are first to enter the unit are also the first to exit the unit to minimize residence time and reduce the likelihood that solid materials will be burned and stick to the apparatus. The solids should also be conveyed through the apparatus with minimum mixing to prevent the grinding or breaking up of the solids as they are conveyed.
The present invention addresses these needs, as well as other problems associated with existing methods and apparatus for removing solvents from solid particles contaminated therewith. The present invention also offers further advantages over the prior art and solves problems associated therewith.